The Lin Process for Flue Gas Desulfurization is designed to effectively remove sulfur dioxide from stack gas in an economical manner. In my recent U.S. Pat. No. 4,975,257, incorporated by reference herein, the recently discovered mechanism of the Lin Process has been revealed The mechanism includes kinetics, a reaction model, the function of water vapor in the reactions, and others. With the understanding of the mechanism, the process can be simplified, resulting in a reduction of capital and operating costs. Referring to the accompanying FIG. 1 which illustrates a bypass flow of flue gas as disclosed in U.S. Pat. No. 4,975,257, the Lin process for retro-fitting a power plant application can be described as follows:
Gas emission from a boiler is treated to separate solid particles such as fly ash, and then split into two flow streams, designated as streams A and B. Stream A is adjusted to the optimum catalytic conversion temperature at about 800.degree. F. before being directed through a catalytic oxidation converter where a large fraction of SO.sub.2 is converted to SO.sub.3. Stream B is by-passed around the catalytic converter and rejoined with stream A at the downstream side of the catalytic converter. The combined gas then enters a fluidized lime reactor where the sulfur dioxide/sulfur trioxide mixture is allowed to react with lime particles. The resulting solid material of the dry scrubbing is called "Linfan", the bulk of which can be separated from the gas and recovered as a valuable by-product. The remaining dust in the exit gas is removed by cyclones or other suitable solids removal devices located at the downstream side of the fluidized reactor. The gaseous effluent leaving the desulfurization process is essentially free of dust and sulfur oxides.
The desulfurization process is a completely dry process that offers numerous advantages over other processes. The process is effective in removing nearly 100 percent of sulfur oxides (SO.sub.2 and SO.sub.3) from the flue gas at temperatures ranging from 500.degree. F. to 900.degree. F. Furthermore, the process is highly exothermic; in passing through the catalytic converter and fluidized lime reactor, the temperature of the flue gas typically increases by 270.degree. F. for each percent of SO.sub.x contained in the gas. The energy generated from the process can be recovered for heating or other purposes.
The resulting solid by-product of the process, Linfan, consists of a core of lime surrounded by a shell of anhydrous calcium sulfate which has a plurality of cracks. The calcium sulfate coating, being formed in high heat from the chemical reactions, is a useful material. It has been proved that Linfan can be used for plastering material, reclaiming fly ash for high-strength construction material, substituting cement in concrete production, as an important ingredient in cement production, and as a chemical for municipal and industrial wastewater treatment. Since the by-product has diversified commercial applications, the process has no waste disposal problem.